11.2 Autoimmune Hepatitis & Metabolic Liver Disease

2. Autoimmune Hepatitis (AIH)

Epidemiology & Immunopathogenesis

Autoimmune hepatitis is an unresolving, chronic necroinflammatory liver disease characterized by circulating autoantibodies, hypergammaglobulinaemia, and interface hepatitis on histopathology. Marked female preponderance (~4:1) with a strong immunogenetic link to HLA-DR3 (associated with aggressive, early-onset disease) and HLA-DR4 (associated with late-onset, indolent disease).

Subtypes of Autoimmune Hepatitis

• Type 1 Autoimmune Hepatitis (~80% of cases):
  • Bimodal age distribution: peaks in adolescence/young adulthood and perimenopause (age 40–60).
  • Serology: Positive Antinuclear Antibodies (ANA) and/or Smooth Muscle Antibodies (SMA), specifically directed against F-actin. Serum immunoglobulin G (IgG) is markedly elevated (polyclonal hypergammaglobulinaemia).
  • Clinical course: Variable, from insidious fatigue and fluctuating jaundice to acute severe hepatitis; responds favorably to systemic glucocorticoid therapy.
• Type 2 Autoimmune Hepatitis (~20% of cases):
  • Primarily affects female children, adolescents, and young adults (age 2–14 years).
  • Serology: Characterized by Anti-Liver-Kidney Microsomal type 1 antibodies (anti-LKM1), directed against cytochrome P450 2D6 (CYP2D6), or Anti-Liver Cytosol type 1 antibodies (anti-LC1). Total IgG may be normal or only mildly elevated.
  • Clinical course: Often presents acutely with severe, aggressive hepatitis; higher rate of acute liver failure, frequent treatment failure, and early progression to cirrhosis.

Histopathological Hallmarks (Liver Biopsy)

Liver biopsy is mandatory for definitive diagnosis, staging, and grading:

1. Interface Hepatitis (Piecemeal Necrosis): Dense inflammatory infiltrate extending from portal tracts across the limiting plate into the surrounding lobular parenchyma, causing apoptotic destruction of periportal hepatocytes.
2. Plasma Cell Infiltration: Marked predominance of mature plasma cells and T-lymphocytes within the portal tracts.
3. Hepatocyte Rosetting & Emperipolesis: Hepatocytes arranged in pseudo-rosettes around collapsed reticulin fibres; active penetration of intact lymphocytes into the cytoplasm of viable hepatocytes (emperipolesis).

Pharmacological Management

• Induction of Remission: High-dose oral prednisolone (30–40 mg daily, tapered over 4–8 weeks based on biochemical improvement). In non-cirrhotic patients with mild disease, oral budesonide (9 mg daily) may be used to minimize systemic steroid toxicities due to high (~90%) first-pass hepatic metabolism (strictly avoided in cirrhosis due to portosystemic shunting bypassing hepatic clearance).
• Maintenance Therapy: Oral azathioprine (1–2 mg/kg/day) is added once transaminases decline to maintain remission and permit steroid withdrawal. Thiopurine methyltransferase (TPMT) activity or genotype must be established prior to initiating azathioprine to prevent lethal bone marrow aplasia. Maintenance therapy is continued for a minimum of 2–3 years; premature cessation leads to high relapse rates (>70–80%). Second-line immunosuppressants include mycophenolate mofetil (MMF) or tacrolimus.

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3. Metabolic Liver Diseases

Hereditary Haemochromatosis (HH)

• Genetics & Molecular Pathophysiology:
  • Autosomal recessive disorder of iron homeostasis caused by mutations in the HFE gene on chromosome 6p21.3 (HLA-linked). The most common mutation is C282Y homozygosity (substitution of tyrosine for cysteine at amino acid position 282), accounting for ~85–90% of clinical cases. Compound heterozygotes (C282Y / H63D) exhibit lower penetrance.
  • Mechanism: Wild-type HFE protein regulates iron sensing by forming a complex with transferrin receptor 1 (TfR1) on hepatocytes, stimulating the transcription of hepcidin (the master iron-regulatory hormone). Mutant HFE fails to traffic to the plasma membrane, resulting in inappropriately low hepcidin synthesis. Low hepcidin leads to uninhibited, continuous cell-surface expression of ferroportin (the principal basolateral iron export channel on duodenal enterocytes and reticuloendothelial macrophages). Consequently, duodenal iron absorption surges uncontrollably (2–4 mg/day vs physiological 1 mg/day), saturating transferrin and resulting in toxic parenchymal accumulation of non-transferrin-bound free iron (haemosiderin) in the liver, pancreas, heart, joints, and pituitary gland.
• Clinical Manifestations: Classically presents in males aged 40–60 years (delayed in females until postmenopause due to physiological iron loss via menstruation and childbirth):
  • Hepatic: Hepatomegaly, elevated transaminases, micronodular cirrhosis, and an extraordinarily high risk of hepatocellular carcinoma (HCC, 20- to 200-fold increase). Exam rule: Even after complete iron depletion via venesection, patients with pre-existing cirrhosis retain a persistently elevated lifetime risk of HCC, requiring lifelong 6-monthly ultrasound surveillance.
  • Endocrine & Cutaneous ("Bronze Diabetes"): Slate-grey or bronze cutaneous hyperpigmentation (melanin hypersecretion combined with dermal haemosiderin deposition) and diabetes mellitus secondary to iron deposition within pancreatic beta-islet cells.
  • Musculoskeletal Arthropathy: Present in ~50% of patients. Classically affects the second and third metacarpophalangeal (MCP) joints and wrists, manifesting with pain, stiffness, bony enlargement, and hook-like osteophytes. Plain radiography reveals joint space narrowing, subchondral cysts, and chondrocalcinosis (calcium pyrophosphate dihydrate [CPPD] / pseudogout). High-yield fact: Arthropathy does NOT improve with venesection therapy!
  • Cardiovascular: Dilated cardiomyopathy (less commonly restrictive pattern) with congestive heart failure and cardiac conduction abnormalities / refractory tachyarrhythmias (atrial fibrillation, supraventricular tachycardia). Cardiac dysfunction is reversible with timely iron removal.
  • Endocrine (Pituitary): Anterior pituitary iron deposition causes hypogonadotrophic hypogonadism (loss of libido, erectile dysfunction, testicular atrophy, amenorrhoea).
• Diagnostic Pathway:
  • Initial Screening Investigation: Fasting Transferrin Saturation (serum iron / total iron-binding capacity [TIBC]). A value >50% in females or >55% in males is the most sensitive and earliest biochemical abnormality.
  • Serum Ferritin: Marker of total body iron storage. Ferritin >1000 ug/L strongly correlates with advanced hepatic fibrosis or cirrhosis and warrants formal fibrosis staging.
  • Confirmatory Genetic Testing: Targeted PCR for HFE mutations (C282Y and H63D).
  • Liver MRI (T2 Gradient Echo):* Accurately quantifies hepatic and myocardial iron concentration non-invasively.
• Therapeutic Management:
  • Therapeutic Venesection (Phlebotomy): First-line treatment. Weekly or fortnightly removal of 500 mL of whole blood (~250 mg elemental iron) until the induction target is reached: serum ferritin 50–100 ug/L and transferrin saturation <50%. Thereafter, lifelong maintenance venesection is performed every 2–4 months to maintain ferritin between 50–100 ug/L.
  • Iron Chelation: Reserved strictly for patients with severe anaemia, severe cardiac failure, or poor venous access where venesection is contraindicated. Oral deferasirox or subcutaneous deferoxamine.

Wilson's Disease (Hepatolenticular Degeneration)

• Genetics & Pathophysiology:
  • Autosomal recessive disorder caused by loss-of-function mutations in the ATP7B gene on chromosome 13q14.3, encoding a copper-transporting P-type ATPase.
  • Mechanism: ATP7B mediates two critical intrahepatic processes: (1) transport of copper into the trans-Golgi compartment for incorporation into apocaeruloplasmin to synthesize mature caeruloplasmin, and (2) trafficking to the canalicular membrane to excrete excess copper into bile. Defective ATP7B blocks biliary copper excretion and prevents caeruloplasmin synthesis. Toxic copper accumulates inside hepatocytes; when storage capacity is saturated, free non-caeruloplasmin-bound copper spills into the systemic circulation and deposits pathologically in the brain (basal ganglia), cornea, and kidneys.
• Clinical Presentation: Typically manifests between the ages of 5 and 35 years:
  • Hepatic Manifestations (Younger Patients, ~Age 10–15): Acute hepatitis, chronic active hepatitis, cirrhosis, or acute liver failure. Acute Wilsonian liver failure characteristically presents with Coombs-negative intravascular haemolytic anaemia (due to massive free copper release lysing red blood cells), an exceptionally low alkaline phosphatase (ALP/bilirubin ratio <2.0), and an AST/ALT ratio >2.2.
  • Neuropsychiatric Manifestations (Older Patients, ~Age 15–30): Copper accumulation in the lenticular nuclei (putamen and globus pallidus) produces basal ganglia dysfunction. Dysarthria is the single most common initial neurological symptom. Other features include dystonia, Parkinsonian rigidity, masked facies, resting and postural "wing-beating" tremor, chorea, ataxia, personality deterioration, mood swings, depression, and frank psychosis.
  • Ophthalmic Hallmarks: Kayser-Fleischer (KF) rings—golden-brown, greenish-brown copper deposits in Descemet's membrane at the corneal limbus. Identified via slit-lamp biomicroscopy; present in >95% of patients with neurological Wilson's disease (but only ~50% with purely hepatic disease). "Sunflower" cataracts may also be observed.
  • Renal Tubular Dysfunction: Proximal tubular copper toxicity producing Fanconi syndrome (glycosuria, aminoaciduria, phosphaturia, renal tubular acidosis).
• Diagnostic Investigations:
  • Serum Caeruloplasmin: Reduced (<0.20 g/L; normal 0.20–0.40 g/L). Crucial exam caveat: Caeruloplasmin is an acute-phase reactant; levels may be falsely normal during active hepatic necroinflammation, pregnancy, or estrogen therapy.
  • 24-Hour Urinary Copper Excretion: The most sensitive non-invasive screening investigation. Exceeds >1.0 umol/24 hours (>60–100 ug/24 hours) in symptomatic disease.
  • Elevated Serum Free (Non-Caeruloplasmin-Bound) Copper: >25 ug/dL.
  • Slit-Lamp Examination: Confirms Kayser-Fleischer rings.
  • Liver Biopsy: Gold standard for equivocal cases; shows quantitative hepatic copper concentration >250 ug/g dry weight (normal <50 ug/g).
• Management Strategy:
  • Copper Chelation Therapy: Initial decoppering with D-Penicillamine (chelates copper and promotes urinary excretion; co-prescribe pyridoxine / vitamin B6 to prevent deficiency; watch for nephrotoxicity, bone marrow suppression, and myasthenia-like syndromes) or Trientine dihydrochloride (preferred initial agent due to superior adverse effect profile and lower risk of neurological worsening).
  • Maintenance Therapy: Oral zinc salts (zinc acetate or zinc sulphate); zinc induces enterocyte metallothionein, which avidly binds dietary copper in intestinal epithelial cells, preventing systemic absorption and causing it to be shed in faeces.
  • Liver Transplantation: Curative for acute liver failure (King's College prognostic score >=11) or end-stage decompensated cirrhosis; replaces the defective ATP7B enzyme.

Alpha-1 Antitrypsin Deficiency (A1ATD)

• Genetics & Allelic Variants:
  • Autosomal codominant disorder caused by mutations in the SERPINA1 gene on chromosome 14q32.1, encoding alpha-1 antitrypsin (A1AT), an acute-phase serine protease inhibitor (serpin).
  • Normal allele is PiM (Protease inhibitor M). Deficiency alleles include PiS (mildly reduced) and PiZ (severely reduced; caused by a Glu342Lys point mutation).
    • PiMM: Normal homozygous phenotype (100% circulating A1AT activity).
    • PiMZ: Heterozygous carrier (~50–60% normal levels; minimal disease risk in isolation).
    • PiZZ: Homozygous severe deficiency (~10–15% normal circulating levels; high risk of juvenile cirrhosis and premature emphysema).
• Pathophysiology:
  • Hepatic Pathology (Toxic Gain-of-Function): The Z-mutant protein undergoes abnormal conformational folding, forming insoluble polymers that become trapped inside the rough endoplasmic reticulum of periportal hepatocytes. The trapped aggregates induce chronic endoplasmic reticulum stress, autophagy exhaustion, and hepatocyte apoptosis, resulting in neonatal cholestasis, chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Key MRCP concept: Liver disease results from toxic intracellular protein accumulation, NOT from a lack of circulating antiprotease activity!
  • Pulmonary Pathology (Loss-of-Function): In the lungs, profound deficiency of circulating A1AT leaves neutrophil elastase uninhibited, leading to unrestrained proteolytic destruction of alveolar elastin. Results in premature, severe panacinar (panlobular) emphysema, predominantly affecting the lower lung zones (bases), markedly accelerated by cigarette smoking.
• Histopathology: Diagnostic hallmark on percutaneous liver biopsy is the presence of intracellular, round, eosinophilic periodic acid-Schiff (PAS)-positive, diastase-resistant globules within periportal hepatocytes.
• Diagnostics & Management: Quantitative serum A1AT level; confirmatory phenotyping via isoelectric focusing or SERPINA1 genotyping. Smoking cessation is absolute. Intravenous human A1AT augmentation therapy slows emphysema progression. Liver transplantation cures the hepatic disease and the systemic biochemical defect (donor graft expresses the PiMM phenotype).

Non-Alcoholic Fatty Liver Disease (NAFLD / MASLD)

• Nomenclature & Spectrum: Renamed Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). Defined by hepatic steatosis in the presence of at least one cardiometabolic risk factor (type 2 diabetes, obesity, dyslipidaemia, hypertension) without significant alcohol consumption (<20 g/day for women, <30 g/day for men).
  • Metabolic Dysfunction-Associated Steatohepatitis (MASH / NASH): Characterized histopathologically by the triad of: (1) macrovesicular steatosis (>5%), (2) hepatocyte ballooning degeneration, and (3) lobular inflammation with Mallory-Denk bodies and pericellular / perisinusoidal ("chicken-wire") fibrosis.
• Non-Invasive Fibrosis Stratification:
  • FIB-4 Index: Non-invasive score derived from: [Age x AST] / [Platelets x sqrt(ALT)].
    • FIB-4 <1.30: High negative predictive value (>90%) ruling out advanced fibrosis (stage F3–F4); managed in primary care with lifestyle optimization.
    • FIB-4 >2.67: High positive predictive value for advanced fibrosis; warrants prompt secondary care referral for transient elastography (FibroScan) or specialist hepatology evaluation.
  • NAFLD Fibrosis Score (NFS): Incorporates age, BMI, impaired fasting glucose/diabetes, AST/ALT ratio, platelet count, and serum albumin.
  • Transient Elastography (FibroScan): Measures liver stiffness (LSM in kPa; <8 kPa rules out advanced fibrosis; >12–15 kPa indicates cirrhosis) and Controlled Attenuation Parameter (CAP in dB/m) to quantify steatosis.
• Management: Lifestyle modification targeting 7–10% total body weight loss (promotes histological MASH resolution and fibrosis regression); optimization of metabolic co-morbidities (GLP-1 receptor agonists e.g., semaglutide; SGLT2 inhibitors; statins are safe and indicated to reduce cardiovascular mortality); resmetirom (thyroid hormone receptor-beta agonist) indicated for non-cirrhotic MASH with moderate-to-advanced fibrosis.